Sound apparatus



mwm 399 Egg? A. DU BOiS-FZEYMOND S-OUND APPARATUS Filed March 24. 1921Patented Aug. 30, 1927.

UNITED STATES 1,640,538 PATENT OFFICE.

ALABD DU BOIS-REYMOND OF PLON', NEAR KEL, PRUSSIA, GERMANY, ASSIGNOB TOTHE FIRM SIGNAL GESELLSGHAFT M. B. 3., 01 KIEL, GERMANY.

SOUND APPARATUS.

Application filed March 24, 1921, Serial No. 455,321, and inGermany.August 6, 1917.

In the construction of electromagnetically driven or operating soundapparatus, for example, electromagnetic submarine sound transmitters orreceivers, the necessity often arises of fastening current coils ofvarious kinds on the oscillating structures or systems of the apparatus.The invention is based on the recognition of the fact that the simplefastening of the coils on the oscillating structures or systems isunsatisfactory, in

that the wires surrounded with insulating material form aloosefstructure in the acoustic sense which strongly damps the oscillatory system. Furthermore it is not feasible devised and will behereinafter described in detail. The technical carrying out of theinvention can be eifected in different ways; either by building thecoils themselves, and the oscillatory structures carrying them, togetheras a rigid mass, or by choosing a method of fastening the coils whichobviates an acoustically injurious action of the same on the oscillatorystructure. In the first case in the design of the oscillatory structitrethe additionalmass formed b the coil must be taken into consideration.ther and further objects of the invention will appear or be pointed outhereinafter.

The rigid fastening above referred to is efiected, for example, bycasting the coil parts with binding material (resin, bakelite, or thelike) so as to form a rigid structure,

and then casting with suitab e matrix drilled grooves, slots or thelike.

Suitable means for mounting the coils on the oscillatory structure orfor mounting the ,coil carriers on the oscillatory structure for thepurpose of acoustically insulating these parts may be effected by theinterposition of non-rigid fastening means or intermediate layers withno appreciable elastic action or of such a nature as to form a structuretuned so low as to have a natural frequency much below the natural orcoupling frequencies of the oscillatory structure or system. Thus, forexam le, the coils (to be hereinafter referred to? may be surrounded byor encased in such materials as rubber,

.structed in accordance with the of my invention and in which theinterstices between the windings are filled in with suitable materialfor binding them together. The coil is thus cast in.

Figure 2 shows in section an electro-magnetic sound apparatus with achoking coll attached to, the electromagnet system by springs. 1

Figure 3 shows in modified form an axial section at right angles toFigure 2 disclosing in detail the method of supporting the 4 coil 5.

In Figure 1, 1 indicates a sound diaphragm, 2 and 3 the armature andelectroma et of an electromagnetically operatin oscillatory structure,and 4 sprin s by whic the parts 2 and 3 are connecte with one another. 5is the exciting coil which lies in slotsin the field magnet 3 and iscast therein by means of an embedding mass 6.

According to the embodiment of my in-, yention shown in Figures 2 and 3,an auxiliary ap aratus may, when necessary, be mounte upon the vibratorystructure without causing in 'urious damping eflects. Thus, a chokingcoi 7 with a laminated iron core 8 is held by the carrier 9. The latteris ided on me 10 which'are rigidl seated in the principles withthe'iron' core carried by it engages against the carrier itself throughsoft layers 12 of indiarubber or the like. The excitin coils 5 of theelectro-magnet are here (11- vided into an alternating current coil anda direct current coil, and in the current circuit of the latter thechoking coil is connected.

The purpose of this construction will be readily understood. By aninspection of Figures 2 and 3, it will e seen that the construction issimllar to that in a transformer having a closed magnetic circuit. Income are obtained when the number of turns vin the direct currentwinding is made about ten times as great as the number of turns in the.

alternating current winding. Such a ratio in the numbers of turns inthese windings, how-.

ever produces an alternating current potential 111 the direct currentcoil ten times as large as that in the alternating current coil and thusoccasions a new difliculty. To overcome this difliculty, the chokingcoil? is connected up in circuit with the direct current winding for thepurpose of confining the high Voltages to those conductors which aredisposed entirely within the casing 13. This is shown in Fig ure 2 wherethe Wire 20 goes from the choke coil 7 to the winding 5 while the wire21 connected to the other end of the winding 5 passes through thecasing. The other lead 22 connects directly to the choke coil 7 so thatthe choke coil 7 and the direct current winding 5 are in series. 'As aresult, the question of insulationas related to those wires which passinto and out of the casing becomes a comparatively simple one.

Another feature of the construction of Figures 2 and 3 is that all theoperating parts are contained within a casing, a portion of the wall ofwhich is formed by the dia hragm 1 and another portion of the wall ofwhich is formed by the removable or detachable cap 13, and that thesearts are carried or supported by the diap ragm 1 free from the cap 1.This feature of construction makes it possible to remove the cap withoutdisturbing interior connections, so that ins ection of the operatingparts may readily had.

I claim: a

1. In acoustic apparatus, in combination, a vibrato diaphragm, avibratory structure carried y sa1d diaphragm, an electric coil, andmeans whereby said coil is carriedby sa'idvibratory structure but isacoustically insulated therefrom.

2. In acoustic apparatus, in combination, a vibratory diaphragm,'avibratory structure in the form of an electro-magnet carried by sa1ddlaphragm, an electric coil, and means whereby said coil is carried bysaid elcctro magnet but is acoustically insulated therefrom.

3. In acoustic apparatus, in combination, a vibratory diaphragm, avibratory structure in the form ofan electro-magnet carried by saiddiaphragm, a direct current polarizing coil for said electro-magnet, analternating current exciting coilfor said electromagnet, a choke coilfor'said polarizing coil circuit,'and means whereby said choke coil iscarried by said electro-magnet but is ac'oustically insulated therefrom.

4. In acoustic apparatus, in combination, a vibratory diaphragm, avibratory structure carried by said diaphragm, an electric coil, andmeans supporting said coil on said vibratory structure, sa-id meansbeingof such resiliency asto acoustically insulate the coil from saidvibratory structure.

5. In acoustic apparatus, in combination, a vibratory diaphragm, avibratory structure carried by said diaphragm, an electric coil,

and means SHPPOIlJlIl said coil on said vibratory structure, sai meanshaving a natural frequency considerably below that executed by saidvibratory structure, whereby the coil is acoustically insulated fromsaid vibratory structure. i

6. In acoustic apparatus, in combination, a casing, a vibratorydiaphragm forming a portion of the wall of said casing, 21 removable capforming the remaining portion of the Wall of said casing and completelyclosing the apparatus, a vibratory structure carried by said diaphragm,an electric coil, and means whereby said coil is carried by saidvibratory structure but is acoustically insulated therefrom; the saidvibratory structure and coil being supported by said diaphragm free fromthe removable cap of said casing.

7. In acoustic apparatus, in combination, a casing, a vibratorydiaphragm forming a portion of the wall of said casing, a removable capforming the remaining portion of the wall of said casing andcon'ipletely closing the up )aratus, a vibratory structure in the form 0an electro-magnet carried by said diaphragm, a direct current polarizingcoil for said electro-magnet, an alternating current exciting coil. forsaid electro-magnet, a choke coil for said polarizing coil circuit, andmeans whereby said'choke coil is carried by said electro-magnet but isacoustically insulated therefrom; the said electromagnet and coils beingsupported by said diaphragm free from the removable cap of said casing.

In test-imonywhereof I afl'ix my signature.

ALARD DU BOIS-REYMOND.

